Each screw design is an exercise in finding the "sweet spot." Each polymer, each extruder, and each process requires a different design to optimize performance. First to be considered are the capabilities of the extruder, including horsepower, screw speed, bore size, L/D, etc. Then the requirements for the process come into play, such as the desired melt temperature, output, need for devolatil-ization, homogeneity of the melt, and the stability of output. Finally the thermal, rheological, and solid particle properties of the polymer must be considered. I've designed thousands of single screws and can say emphatically that there are few exact duplicates among them, due to all these considerations.
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